1. Field of the Invention
The present invention is directed to the production of polysaccharides and polysaccharide derivatives and, in particular, compositions, tools, systems and methods for the stabilization of clays, shales and other clay-containing materials and soils with polymers containing dextran, dextran derivatives, and other substituted polysaccharides.
2. Description of the Background
Clay poses challenges, as it is well known for swelling in the presence of water. Within its crystalline layers, clay contains cations, typically sodium, which occupies base-exchange sites. Upon contact with water, these cations are solubilized resulting in clay instability and often swelling with complete breakdown of the solid into liquid slurry. When clay swells with the absorption of water, there is surface swelling and/or osmotic swelling due to absorption.
The ability of the clay-containing land to permit drilling, passage of liquids, or fracturing fluids as well as hydrocarbons, is diminished, impeding production. A number of clay stabilizers are available such as potassium chloride which functions in an ion exchange process. Potassium chloride reduces clay swelling by replacing a native clay cation with a potassium ion and/or creating an overall negative charge on individual clay layers. This charge is compensated for by cations located in the interlayer region, which can be freely exchanged. Accordingly, potassium saturated clays have a reduced tendency to swell and absorb liquids, thus increasing the excavation process and reducing excavation costs.
The cation exchange capacity of the mineral depends on crystal size, pH, and the particular type of cation involved. These may not only be small ions, but also poly-cations. Also, the potassium ion is over seventy percent larger than the sodium ion. Although potassium ions are effective at preventing swelling, high levels are required which contaminates the area. In addition, potassium chloride is hazardous and incompatible with other materials used, for example, in drilling and mining operations. Potassium negatively impacts fracturing fluids such guar, xanthan, welan, scleroglucan and polyacrylamide polymers, each of which is utilized in one or another excavation process.
Accordingly, there is a need in the art for a safe and effective clay stabilizer which is effective in all or substantially all of the clay constituents in a heterogeneous clay/shale formation.